A6985F datasheet(51/77 Pages) STMICROELECTRONICS

Part #	A6985F

Description	38 V 500 mA synchronous step-down switching regulator

PDF	77 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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51 / 77 page

DocID027738 Rev 2

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A6985F

Application notes

Figure 39. Slave to master mode transition

The external master can force a latched SLAVE mode driving the SYNCH pin low at power-

up, before the soft-start starts the switching activity. So the oscillator frequency is 250 kHz

typ. fixed until a new UVLO event is triggered regardless FSW resistor value, that otherwise

counts to design the slope compensation. The same considerations above are also valid.

The master driving capability must be able to provide the proper signal levels at the SYNCH

pin (see Table 5 on page 8 - Synchronization section):

 Low level < VSYN THL= 0.7 V sinking 5 mA

 High level > VSYN THH = 1.2 V sourcing 0.7 mA

Figure 40. Master driving capability to synchronize the A6985F

250kHz typ.

SLAVE mode

stand alone operation at nominal fsw

SYNCH signal

switching node

A6985F Datasheet(PDF) 51 Page - STMicroelectronics